Hydropumping of hydrocarbon slurries over large distances is often carried out by pumping such slurries through large diameter (often 36 inch/0.3 m or greater) pipe segments which make up an “oil” pipeline.
Due to the highly-abrasive nature of some of the slurries (such as bitumen when recovered from a tar sands recovery facility and which typically contains a substantial amount of abrasive sand), frequently elongate narrow-diameter (ie 0.25 in/0.63 cm) abrasion-resistant chromium carbide rods (alternatively called “wires”) are welded to the interior of each pipe segment making up a pipeline, with a multitude of such carbide rods extending longitudinally the length of the pipe and radially juxtaposed about the entire circumference of the interior of each pipe segment to thereby cover the entirety of the inner periphery of each pipe segment and thereby increase the wear resistance of the interior of each mild-steel pipe segment to abrasion. Alternatively, such wires may be circumferentially wound around the inner periphery of the pipe.
Pipes having the above chromium-carbide rods have been found to have increased abrasion resistance between 4 to 14 times as compared to the lifespan of ordinary mild steel pipe which lack chromium carbide rod overlays.
The applicant Indutech Canada Ltd., using various specially-adapted equipment and techniques, has for many years manufactured and supplied abrasive-resistant piping having such chromium carbide rod overlays welded to the interior of pipe segments, where such pipe segments are to be used in hyrdopumping of slurries of crude oil and bitumen and where such slurries are abrasive in nature.
Problematically, however, chromium carbide rods typically have a substantially different co-efficient of thermal expansion than the outer steel pipe. Accordingly, during welding of the inner chromium carbide rods to the interior of the steel pipe and also when a mating flange is welded to the pipe, the pipe inner diameter becomes non-concentric and distorted (out of round). Moreover, due to the rod-like nature of the rods when welded to the interior of the pipe, discontinues due to the non-uniform nature of the rods exists.
This distortion and discontinuities between pipe segments is extremely undesirable, since when bolting a pipe-flange assembly of one pipe segment to another similar pipe flange assembly of another pipe segment in order to form a continuous pipeline, any distortion in the circular contour of the inner pipe diameter at its mating edge with another flange assembly results in discontinuities in the interior surface of the pipe. Such discontinuities undesirably cause turbulence in the flow of the slurry within the pipe. Accordingly, when abrasive slurries are pumped through the pipe, undesirable and increased wear on the interior of the pipe occurs at the areas of non-concentricity. This results in greatly increased friction and wear at the points of discontinuity.
In addition to the detrimental effect on pipe wear life due to increased wear, discontinuities in the pipe connections undesirably cause turbulence, which reduces the extent to which there is laminar flow of fluid in the pipeline. Laminar flow in the pipeline (as opposed to turbulent flow) is greatly desired, as laminar flow results not only in less wear within the pipeline, but decreases the pumping pressure necessary to pump a hydrocarbon slurry over a given distance. Accordingly, discontinuities in the interior pipe diameters at the point of coupling of one pipe section to another results in higher pump pressures (and larger pumps) necessary than would otherwise be the case if laminar flow was achieved to a greater degree in the pipeline.
In order to attempt to reduce the above problems, pipeline companies when purchasing abrasive-resistant piping frequently specify that the concentricity and diameter of each mating flange be within certain strict tolerances, in order to reduce or eliminate to the extent possible the above undesirable conditions.
Accordingly, to meet the strict tolerances and concentricity requirements of the pipe segment flanges and to thereby avoid the undesirable occurrence of discontinuities in the slurry flow from one pipe segment to another, skilled welders are required to “build up” the inner circular diameter of each pipe segment proximate each flange member to a greater degree than necessary (ie with an excess carbide rods or weld material), and then grind down the “high” areas of the “overlay” to make the interior of the pipe flange of a fixed diameter and perfectly circular and concentric, so that when a similar flange is bolted to it there is a smooth transition at the point of abutment of the two pipe segments, and no turbulent flow is created.
Unfortunately, however, “building up” the inner area in such manner and then grinding out the “high” spots to obtain a perfectly circular and concentric inner pipe requires great skill, but even more problematically, is difficult to do and extremely time consuming and thus introduces considerable expense to the cost of manufacture of wear and abrasion-resistant pipe.
Accordingly, a real need exists in the art of manufacture of abrasion-resistant pipe for an apparatus and method to more rapidly (and in a less labour-intensive and costly manner) produce abrasive-resistant pipe wherein the inner diameter (at least in the region of the mating flange) is concentric with and in a substantially uniform fixed diametric relation with the circular outer periphery and/or bolt hole pattern on the associated flange member, in order to reduce or eliminate discontinuities in the interior of the resulting pipeline formed by the joining of various abrasion-resistant pipe segments.
U.S. Pat. No. 4,850,524 entitled “VERTICAL STRIP CLAD WELDING METHOD AND APPARATUS” teaches a method and apparatus for welding vertical strip clad overlays into interiors of cylindrical vessels. Insofar as is potentially relevant, such apparatus teaches, at col 3, lines 54-60, a welding shoe 70 which comprises a shoe mold 72 and a shoe insert 74. The should mold 72 is preferably of copper, and has cooling passage 75 therein to permit cooling of the welding shoe. Notably, however, the purpose of the device disclosed in U.S. Pat. No. 4,850,524 is to weld strip cladding, and there is no disclosure nor provision on the weld apparatus to situate itself concentrically to a flange bolt pattern or circular outer periphery of a flange for the purpose of ensuring concentricity of the inner diameter of the cylinder with a bolt flange pattern.
US Publication 2008/0048010 entitled “CLADING COMPLEX PIPING GEOMETRY” teaches a mounting fixture for weld equipment used in weld overly operations on nozzles of a nuclear power generator pressurizer. The mounting fixture has a first ring which is adapted to be located around pressurizer pipe, having such mounting assemblies thereon for mounting to studs welded to a surface of the pressurizer, and a second region spaced from the first ring, having a series of jacking assemblies which can be positioned against the pipe nozzle, and a series of support legs (item 46, FIGS. 3&4) connecting the first and second ring.
U.S. Pat. No. 6,953,142 entitled “METHOD AND APPARATUS FOR HOLDING A FLANGE” discloses an apparatus for locating and grasping a flange, having a number of clamp arms. Importantly, a number of pins are adapted to move upwardly into flange holes within the flange for positioning the flange during the clamping action. Accordingly, the mounting fixture of U.S. Pat. No. 6,953,142 is not for mounting on the interior of a flanged pipe to ensure uniform concentric deposition of weld material around the interior of a pipe, and thus this patent likewise is only of background interest.
U.S. Pat. No. 4,496,097 entitled “AUTOMATIC BELLOWS WELDER AND METHOD FOR USING SAME”, as shown in FIGS. 3 & 4 thereof and as described at col. 3, lines 11-35, relates to a welding apparatus for welding two circular plate members along a concentric annulus thereof to form a “convolution”. A pair of planar spaced-apart weld spools 22, and a pressure roller 20 are provided, each arranged in a triangular configuration While the pressure roller 20 forces the diaphragms against the weld spools 22 and ultimately against each other to permit welding. While such is somewhat analogous to the present invention as set out below which uses a pair of rollers on the outside of the flange and the chill block as the effective pressure roller 20, notably, as expressly stated at col. 4, lines 35-40, such device “does not provide for chill . . . [as] it has been found that by this method of fixturing . . . chill can be eliminated.” Moreover, such patent does not teach the spacing of any chill block a spaced distance to allow deposition of weld material, but merely welds two flange type members together to form a bellows.
U.S. Pat. No. 5,942,289 entitled “HARDFACING A SURFACE UTILIZING A METHOD AND APPARATUS HAVING A CHILL BLOCK”, as may perhaps be most clearly seen from FIGS. 2 & 3 thereof, relates to a method and apparatus for deposition of a hardfacing material 60 on a curved (see surface 42 below) surface (see surface 42). A chill block 50, which has a radius approximately equal to (but greater) than the curved surface on the workpiece upon which metal is to be deposited, is provided. The deposition head 48 and chill block 50 in a preferred embodiment are supported together in fixed relation to each other and to the workpiece. The pipe 40 is rotated about its cylindrical axis, and molten material is deposited on the exterior of the pipe 40. Notably, however, there is no triangular “fixation” of the chill block, on the interior of the pipe so as to maintain concentricity with an exterior flange, since the exterior of the pipe receives the deposition.
Lastly, U.S. Pat. No. 6,711,804 entitled “MACHINING CENTER” teaches a machine center, having at least one work spidle unit which is mounted to orbit a central axis. The spindle can be positioned in a plurality of positions around the central axis, and may be moved in the radial direction relative to the central axis. The purpose of the radial mobility of the work spindle unit is to permit location of tools along various partial central path segments, for contact with the workpiece. Such patent does not teach an apparatus having exterior rollers (for positioning on the exterior flange of a pipe), nor an interior chill block which has a spring to bias it (against the interior of the pipe and thus concentrically within the pipe).
Accordingly, and despite the above prior art, a real need continues to exist in the art of manufacture of abrasion-resistant pipe for an apparatus and method to more rapidly (and in a less labour-intensive and costly manner) produce abrasive-resistant pipe wherein the inner diameter (at least in the region of the mating flange) is concentric with and in a fixed uniform diametric relation with the circular outer periphery and/or circular bolt hole pattern on the associated flange member, in order to reduce or eliminate discontinuities in the interior of the resulting pipeline formed by the joinder of various abrasion-resistant pipe segments.